<html>
<head>
    <style>
        body {
            font-family: Arial,Helvetica,"Helvetica Neue",sans-serif;
            color: #444;
        }
        .centered {
            text-align: center;
            display: flex;
            flex-direction: column;
            justify-content: center;
            height: 100%;
        }
    </style>
</head>
<body>
    <div class="centered">
        <h1>There is no help installed</h1>
        <h2>please, download it from <a href='#'>www.onlyoffice.com</a></h1>
    </div>
</body>
</html>